1. Field of the Invention
The invention relates generally to the field of voltage controlled oscillators. More particularly, the invention relates to a cross-coupled cascode voltage controlled oscillator.
2. Discussion of the Related Art
A voltage controlled oscillator (VCO) is a circuit that generates an oscillating signal at a frequency proportional to an externally applied control voltage. These types of circuits find several applications in telecommunications, and are useful for tracking and matching signal frequencies as they shift due to thermal variations, power supply fluctuations, and other sources of frequency shifts.
Typically, a VCO comprises a resonant circuit coupled to an amplifier circuit. The amplifier design can be critical since modern electronics often requires a VCO to operate with a large signal swing or amplitude. A problem with current technology is that large signal operation often causes voltage breakdown processes.
In the prior art, drain to gate voltage breakdown problems that occur in the amplifier circuit of a VCO have been solved by reducing the supply voltage and/or using higher breakdown parts. Nevertheless, these measures tend to reduce signal swing and result in degradation of signal-to-noise floor performance, making it difficult to meet the far-out noise requirements of several applications. Further, higher breakdown parts may not be available, or may not meet other design specifications.
Until now, the requirements of providing a method and/or apparatus for a voltage controlled oscillator which allows a high signal swing while minimizing breakdown problems have not been met.